Engineering the ultrathin coatings with multifunctional bioactivity based on chitosan-Ag and pectin-Ag nanocomposites for modification of bio-implantable materials

Multifunctional ultrathin coatings are of great interest in biomedical-related fields in order to impart the desired properties, such as biocompatibility and antimicrobial or anti-inflammatory activities, to the surfaces of bio-implantable materials. Herein, a deep insight into the features of the design of chitosan-Ag/pectin-Ag and chitosan-Ag/pectin multilayer films using layer-by-layer (LbL) assembly was considered in detail. It has been determined that film growth regime (linear or parabolic) and elastic properties can be controlled by changing the type of polyanionic component in the multilayer system and the number of bilayers, respectively. The obtained films were characterized using QCM-D, AFM, and XPS. Contact angle measurements and tribological testing were also carried out. LbL films possessed a uniform defect-free surface (roughness <11 nm), excellent hydrophilic properties (water contact angle 45.9 ÷ 61.7°), and good wear resistance. A comprehensive study of the biological properties of LbL films was carried out. It has been demonstrated that multilayer systems exhibited excellent antibacterial activity against B. subtilis (up to 4.1 log reduction) and E. coli (up to 3.9 log reduction) and a considerable radical-scavenging effect (ABTS•+ inhibition reached 27.1 %). LbL films did not induce inflammation and can demonstrate anti-inflammatory action (reduction of induced IL-1β level up to 2.6 times) depending on the structure of chitosan-Ag used as the polycation component. LbL films demonstrated high resistance to nonspecific protein adsorption and good biocompatibility with mesenchymal stem cells (the number of viable cells ∼90 %). An in vivo toxicity study indicated that the obtained multilayer systems do not show acute oral and intraperitoneal toxicity; the irritation action and allergenic activity were also not observed. Our results indicate the prospects of applying LbL films for implant modification based on the complex of their physicochemical and biological properties.